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PubMed1996

Refractory congestive heart failure: overview and application of extracorporeal ultrafiltration.

Congestive heart failure (CHF) from ischemic cardiomyopathy has emerged as an epidemic health problem. The pathogenesis of CHF is characterized by heightened activity of many neuroendocrine factors, including norepinephrine, angiotensin II, and arginine vasopressin, which lead to heightened systemic vascular resistance and further impedance of left ventricular ejection. Once CHF reaches New York Heart Association (NYHA) class III or IV with heightened activity of the many neurohumoral factors, it tends to be refractory to conventional therapy of vasodilators, inotropic agents, and diuretics. Treatment of refractory CHF appears to require a break in the neurohumoral hemodynamic vicious cycle, and ultrafiltration appears able to produce this interruption. Ultrafiltration has been shown to be successful in patients with NYHA class III to VI CHF and urine output less than 1,000 mL/d. It relieves pulmonary edema, reduces ascites and peripheral edema, and enhances the response to subsequent diuretic therapy. In patients with refractory CHF, the ability to provide adequate volume removal, thus improving overall volume status, normalizing filling pressures, and reducing clinical symptoms, offers an improvement in overall quality of life. Early results have shown that ongoing therapy actually may be associated with decreased hospital readmissions or, at the very least, shortened intensive care unit length of stay.

Heart Failure↗

PubMed1998

Evaluation of ultrafiltration failure.

The evaluation of ultrafiltration failure is embarked upon when a patient has persistent problems with symptoms and signs of fluid overload. Fluid overload is a common problem in peritoneal dialysis (PD) patients and the risk of its occurrence increases with time on dialysis. Although often attributed to changes in peritoneal membrane function (membrane failure), there are a number of potential, and frequently more common factors that can contribute to the failure of adequate fluid removal in patients on PD. Many of the causes of ultrafiltration failure may be apparent after an initial informal evaluation. However, if after this the etiology remains unexplained, a systematic approach to the differential diagnosis of this problem can be utilized with the use of the peritoneal equilibration test. Once a diagnosis is confirmed, a logical therapeutic plan can be formulated.

Biological Transport↗

PubMed2003

Minimally invasive technique based on ultraslow ultrafiltration to collect and store time profiles of analytes.

A device is described to collect and store continuously time profiles of analytes over periods of 24 h suitable to sample freely moving individuals (humans and animals). The device consists of a hollow fiber ultrafiltration probe, a long capillary and a nonmechanical unit (a disposable medical syringe) driven by vacuum to withdraw fluid. The principle is that at low rates (< or = 100 nL/min), sample fluid is collected through the ultrafiltration probe into the capillary. A time resolution of less than 5 min over a 24-h collection and storage period was achieved for lactate and glucose. To illustrate an in vivo application, devices were fixed under the wing of freely moving broiler chickens, with subcutaneous or intravenous probe placements. The device can be produced as a disposable, and it may become applied for ex vivo and in vitro monitoring.

Animals↗

PubMed2005

Toward defining the human parotid gland salivary proteome and peptidome: identification and characterization using 2D SDS-PAGE, ultrafiltration, HPLC, and mass spectrometry.

Saliva plays many biological roles, from lubrication and digestion to regulating bacterial and leukocyte adhesion. To understand the functions of individual components and families of molecules, it is important to identify as many salivary proteins as possible. Toward this goal, we used a proteomic approach as the first step in a global analysis of this important body fluid. We collected parotid saliva as the ductal secretion from three human donors and separated the protein components by two-dimensional SDS-polyacrylamide gel electrophoresis (2D SDS-PAGE). Proteins in gel spots were identified by peptide mass fingerprinting, and the results were confirmed by tandem mass spectrometry of selected peptides. Complementing this approach we used ultrafiltration to prepare a low-molecular-weight fraction of parotid saliva, which was analyzed directly or after reversed phase high-performance liquid chromatography separation by using mass spectrometric approaches. MS analyses of 2D SDS-PAGE spots revealed known components of saliva, including cystatins, histatins, lysozyme, and isoforms and/or fragments of alpha-amylase, albumin, and proline-rich proteins. We also discovered novel proteins, such as several isoforms of Zn-alpha-2-glycoprotein and secretory actin-binding protein. MS analyses of the ultrafiltrate showed that the low-molecular-weight fraction of parotid saliva was peptide-rich, with novel fragments of proline-rich proteins and histatins in abundance. Experiments using Candida albicans as the test organism showed that at least one of the novel peptides had antifungal activity. Our results show that saliva is a rich source of proteins and peptides that are potential diagnostic and therapeutic targets.

Adult↗

PubMedDate not supplied

Effect of protein adsorption on the transport characteristics of asymmetric ultrafiltration membranes.

The effects of bovine serum albumin adsorption on the transport characteristics of asymmetric poly(ether sulfone) ultrafiltration membranes were determined using polydisperse dextrans with gel permeation chromatography. Actual dextran sieving coefficients were evaluated from observed sieving data for both the clean and preadsorbed membranes using a stagnant film model. The flux dependence of the actual dextran sieving coefficients was used to evaluate the intrinsic membrane hindrance factors for convective (i.e., sieving) and diffusive transport for the different molecular weight dextrans using classical membrane transport theory. Protein adsorption caused a reduction in both dextran sieving and diffusion, with the magnitude of the reduction a function of the dextran molecular weight and pore size. The effects of adsorption on the specific pore area and the membrane porosity were then determined using a recent model for solute transport through asymmetric ultrafiltration membranes. The data indicate that protein adsorption occurs preferentially in the larger membrane pores, causing a greater reduction in solute sieving compared to the membrane hydraulic permeability and porosity than would be predicted on the basis of either a simple pore blockage or pore constriction model.

Adsorption↗

PubMedDate not supplied

Effects of solution properties on solute and permeate flux in bovine serum albumin-IgG ultrafiltration.

It has been observed that bovine serum albumin (BSA, 69,000 Da) exhibits high rejection in a pH 7.4, 0.15 M NaCl solution containing low concentrations of immuno-gamma-globulins (IgG, 155,000 Da). Although it is apparent that this phenomenon is likely due to the complex interactions of the proteins as well as to simple steric hindrance, it is not clear to what extent these resistances contribute to the solute flux loss. This study investigates how variations in IgG concentration, solution pH, and ionic strength can affect the solute and the permeate fluxes for the ultrafiltration of BSA through 100,000 MWCO cellulosic membranes in a batch cell. The results showed that, unlike cases performed at pH 7.4 in 0.15 M NaCl, the presence of IgG may increase the transport of BSA under certain conditions. This study does show the potential value and insights that will result from further binary protein ultrafiltration research.

Chemical Phenomena↗

PubMedDate not supplied

Separation of protein charge variants by ultrafiltration.

The removal of product variants that form during downstream processing remains a challenge in the purification of recombinant therapeutic proteins. We examined the feasibility of separating variants with slightly different net charge using high-performance membrane ultrafiltration. A myoglobin variant was formed by reaction of the lysine epsilon-amino group with succinic anhydride. Sieving data were obtained over a range of solution conditions using commercial polyethersulfone ultrafiltration membranes. Maximum selectivity of about 7-fold was obtained at very low conductivity due to the strong electrostatic repulsion of the more negatively charged variant. Protein separations were performed by diafiltration. A two-stage process generated solutions of the normal myoglobin (in the permeate) and the charge variant (in the retentate), both at greater than 9-fold purification and 90% yield. These results provide the first demonstration that membrane systems can be used to separate proteins that differ by only a single charged amino acid residue.

Complex Mixtures↗

PubMedDate not supplied

Effect of membrane charge on flow and protein transport during ultrafiltration.

Although several recent studies have demonstrated the importance of electrostatic interactions in ultrafiltration, there have been few quantitative studies of the effects of membrane charge density on protein transport and membrane hydraulic permeability. Data were obtained using a series of charge-modified cellulose membranes, with the surface charge density controlled by varying the extent of addition of a quaternary amine functionality. The membrane charge was evaluated from streaming potential measurements. Protein transmission decreased by a factor of 100 as the membrane zeta potential increased from 0.3 to 6.6 mV. The protein sieving data were in good agreement with a partitioning model accounting for electrostatic effects, while the hydraulic permeability data were consistent with a flow model accounting for the effects of counter-electroosmosis. The results provide the first quantitative analysis of the effects of membrane charge density on the performance of ultrafiltration membranes.

Cytochromes c↗

PubMedDate not supplied

Protein purification by ultrafiltration using a beta-galactosidase fusion tag.

The use of beta-galactosidase (465 kDa) as a fusion tag for ultrafiltration-based protein purification has been investigated. The target protein studied was thermophilic glucose dehydrogenase (157 kDa, GDH) from Thermoplasma acidophilum. An expression vector was constructed comprising the lacZ gene fused to a factor Xa cleavage sequence that was attached to the 5' end of the GDH gene. This gene fusion was expressed in Escherichia coli JM109 to yield a soluble protein that exhibited activities for both enzymes. Cleavage of this fusion protein (622 kDa) by factor Xa gave two smaller proteins that showed individual beta-galactosidase and GDH activity. A two-stage diafiltration process for protein purification was used in an ultrafiltration stirred cell. In the first stage, a 500 kDa membrane was used to retain the fusion protein and transmit smaller E. coli host proteins. Approximately 80% of the GDH activity was retained in this step. Following cleavage, the second stage utilized a 300 kDa membrane to fractionate the beta-galactosidase and GDH. No beta-galactosidase was detected in the permeate solutions, and 97% of the GDH activity was recovered in the permeate.

Chemical Fractionation↗

PubMed2005

Remarkable reduction of irreversible fouling and improvement of the permeation properties of poly(ether sulfone) ultrafiltration membranes by blending with pluronic F127.

Hydrophilic modification of ultrafiltration membranes was achieved through blending of Pluronic F127 with poly(ether sulfone) (PES). The chemical composition and morphology changes of the membrane surface were confirmed by water contact angle, X-ray photoelectron spectroscopy, scanning electron microscopy, and protein adsorption measurements. The decreased static water contact angle with an increase in the Pluronic F127 content indicated an increase of surface hydrophilicity. XPS analysis revealed enrichment of PEO segments of Pluronic F127 at the membrane surface. The apparent protein adsorption amount decreased significantly from 56.2 to 0 microg/cm(2) when the Pluronic F127 content varied from 0% to 10.5%, which indicated that the blend membrane had an excellent ability to resist protein adsorption. The ultrafiltration experiments revealed that the Pluronic F127 content had little influence on the protein rejection ratio and pure water flux. Most importantly, at a high Pluronic F127 content membrane fouling, especially irreversible fouling, has been remarkably reduced. The flux recoveries of blend membranes reached as high as 90% after periodic cleaning in three cycles.

Ether↗

PubMed1998

Virus removal from bioproducts using ultrafiltration membranes modified with latex particle pretreatment.

Ultrafiltration is an attractive process for virus removal from bioproducts owing to its high throughput as well as the fact that the operation is carried out under ambient conditions (damage to proteins is highly limited). The principal concern regarding the adoption of conventional ultrafiltration membranes for virus removal is the possibility of the virus passing through abnormally large pores or surface imperfections on the membrane surface. The chief principle behind the present work is to pretreat the membrane by blocking the abnormally large pores using latex particles. Experimental work was conducted to validate this pretreatment using the bacteriophage phi x 174 as a model virus. The results attained were highly encouraging. Different sizes of latex particles were tested by treating a 100 KD molecular weight cut-off membrane, and the transmission of phage (suspended in buffer) through this membrane assessed. In the absence of any particle pretreatment, a virus clearance of 4.78 log reduction value was observed for this membrane. The transmission of phage through the membrane could be reduced by an order of magnitude using 0.11 micron latex particles, or two orders of magnitude using a combination of 0.11 and 0.50 micron particles. The application of latex particles did not hinder the transport of protein through the 100 KD membrane. Protein sieving coefficients obtained using this membrane were 91%, 16% and 2%, for lysozyme, HSA and IgG, respectively.

Bacteriophage phi X 174↗

PubMed1981

Dynamics of glomerular ultrafiltration following open-heart surgery.

To elucidate how individual determinants might lower the rate of glomerular ultrafiltration (GFR) in some patients following cardiac surgery, we performed hemodynamic measurements and clearance of inulin (as a measure of GFR), PAH (as a measure of effective renal plasma flow [ERPF]), and dextran-40. Two groups of 17 patients each were distinguished by the presence or absence of prerenal azotemia. Glomerular hypofiltration (GFR = 21 +/- 2 vs. 76 +/- 6 ml/min/1.73 m2, P less than 0.001) in the former was accompanied by depressed left ventricular function, arterial pressure, and ERPF (152 +/- 26 vs. 317 +/- 32 ml/min/1.73 m2, P less than 0.001). To determine if factors beside ERPF play a role in lowering GFR, we calculated the efferent oncotic pressure (pie). Failure of GFR to change over a 24-hour period despite increases in ERPF suggested that both patient groups were at filtration pressure disequilibrium (FPD). This condition permits calculation of a unique glomerular ultrafiltration coefficient (Kf). Over a range of pressures for transcapillary hydraulic pressure (deltaP), such that 3 less than or equal to (deltaP - pie) less than or equal to 10 mm Hg (to simulate FPD), Kf was less than 0.08 ml . sec-1 . mm Hg-1 . 1.73 m-2 in azotemic, but exceeded this value in nonazotemic patients. Although a selective reduction of Kf is predicted to lower the fractional clearance of dextrans, these were significant elevated in azotemic relative to nonazotemic patients (molecular radii 30 - 40 A). A theoretical analysis of the latter data suggests that over the foregoing range of FPD, a 15 to 30% decline in deltaP combined with a 30 to 0% reduction in Kf from values in nonazotemic patients best explains the experimental findings in azotemic patients.

Cardiac Surgical Procedures↗

PubMed1983

Ultrafiltration in single isolated human glomeruli.

To determine the ultrafiltration properties of human glomeruli, we induced filtration in vitro and estimated the glomerular ultrafiltration coefficient, Kf or LpA, and the glomerular capillary hydraulic conductivity, Lp, in single glomeruli from 17 human kidneys retrieved for allotransplantation. Cadaver donors ranged in age from 2 to 46 years. Filtration was induced in individual isolated glomeruli by abruptly lowering the protein concentration of the medium surrounding a glomerulus to produce a transcapillary oncotic gradient. The events which occurred were recorded on videotape for analysis. Kf was calculated from the maximum rate of glomerular swelling during filtration. Initial glomerular diameter for the individuals studied ranged from 146 +/- 2 microns (age, 2 years) to 292 +/- 6 microns (age, 42 years). Kf ranged from 5.1 +/- 0.8 to 30.7 +/- 3.0 nl/min . mm Hg and varied directly with donor age and glomerular size. The glomerular filtering area was estimated from the formula A = 3 pi D2 and from morphometrically measured basement membrane surface density. Lp was calculated from Lp = Kf/A. Lp using A = 3 pi D2 (LpD) averaged 3.7 +/- 0.2 microliter/min . mm Hg . cm2. To compare the hydraulic conductivity of glomeruli from children and adults, Lp was also calculated using the total basement membrane area derived from measured surface density (LpS).(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗

PubMed1991

Ultrafiltration and effective peritoneal blood flow during peritoneal dialysis in the rat.

The dependence between maximum net ultrafiltration rate (nUFR) created by 15% dextrose dialysis solution and effective peritoneal capillary blood flow (EPBF) estimated by the diffusive mass transport coefficient (KBD) and peritoneal clearance (Cp) of CO2 gas was evaluated during 30 minute, 15 ml peritoneal dialysis exchanges in anesthetized rats (N = 18). The values of KBD for CO2 suggested a mean EPBF of 1.9 +/- 0.1 (SEM) ml/min for isosmotic exchanges and 2.7 +/- 0.2 ml/min for hyperosmotic ones with a mean maximum nUFR of 0.43 +/- 0.01 ml/min. Cp of CO2 measured after the first five minutes of dwell underestimated EPBF. In normally hydrated rats, maximum nUFR was achieved when the peritoneal filtration fraction was 32 +/- 2%. This value is similar to the glomerular filtration fraction in rats of 30%. Thus, our results indicate the following relationships: EPBF = (approximately 3 x maximum nUFR)/(1 - hematocrit). EPBF was about six times greater than maximum nUFR and exceeded about 57 times nUFR obtained under isosmotic conditions. These differences between EPBF and nUFR suggest normal EPBF is not a major limiting factor for maximum ultrafiltration achieved during peritoneal dialysis.

Animals↗

PubMed1992

Role of the venous system in hemodynamics during ultrafiltration and bicarbonate dialysis.

A reduced venous compliance (VC) and inadequate venoconstriction may impair hemodynamics during hemodialysis, the first by impairing plasma volume preservation and by inducing a steep fall in central venous pressure (CVP) during minor plasma volume loss, the second by inadequate mobilization of hemodynamically inactive blood volume. For the protocol A, the relation between VC, the fall in plasma volume and the decline in central venous pressure (CVP) was assessed in 12 hemodialysis (HD) patients, aged 40 to 74 years, during isolated ultrafiltration (UF). The patients were ultrafiltrated for one hour at an UF rate of 1 to 1.5 liter/hr. VC was measured by strain gauge plethysmography with direct i.v. pressure measurements. CVP was assessed directly via a subclavian catheter. PVP was measured using the serial hematocrit method. VC correlated inversely with the fall in plasma volume (r = -0.66; P less than 0.025) and with the fall in CVP (corrected for UF volume) (r = -0.62; P less than 0.025). In the protocol B, the constriction of veins and resistance vessels was assessed sequentially during isolated UF and during UF combined with bicarbonate HD (UF + HD) by measuring the change in venous tone (VT) and vascular resistance (FVR) of the forearm. Twelve HD patients were studied (age 30 to 64 years). VT and FVR were measured using strain gauge plethysmography. The UF rate was equal during isolated UF and UF + HD (1 liter/hr). In six patients, the measurements were started with isolated UF and in six patients with UF + HD.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1992

Nature and rate of vascular refilling during hemodialysis and ultrafiltration.

The change of blood volume, of blood and plasma density (rho b, rho p) following a short ultrafiltration pulse (duration: 20 min; mean rate -35 ml/min) within the first hour of hemodialysis was analyzed in 13 hemodynamically stable patients (30 single measurements). Protein concentration of refilling volume (7 g/liter) was calculated from its density (1009.25 +/- 3.7 kg/m3, at 20 degrees C) and from the linear relationship between plasma density and protein concentration (cp) of uremic plasma samples (rho p = 1007.46 + 0.2422 x cp). The filtration coefficient (Lp,calc) determined from a relation derived from Starling's hypothesis was 5.6 +/- 1.4 ml/(min.mm Hg.50 kg lean body mass); N = 13, mean +/- SD, minimum 3.2, maximum 8.0. A model describing the dynamics of blood and plasma volume was developed. It was fit to on-line measurements of relative blood volume changes by variation of the filtration coefficient and of initial blood volume (Lp,fit, Vb,fit). The linear regression between Vb,fit and blood volume determined from anthropometry (Vb,calc) was highly significant (r = 0.79, N = 30, P < 0.001). Compared to Vb,calc, Vb,fit was typically increased by 21 +/- 11%, reflecting a fluid overload at the beginning of the treatment. Lp,fit was not different from Lp,calc. Lp,fit significantly increased with blood volume excess. Due to the small but definite protein content of refilling volume, the model accounts for increased blood volume recovery and occasional overshoot of blood and plasma volumes following ultrafiltration.

Adult↗

PubMed1977

Preparation and properties of co-reticulated invertase supported by an ultrafiltration membrane.

Yeast invertase was co-reticulated with glutaraldehyde to bovine serum albumin to give a soluble bound enzyme that was immobilized as a tightly adhering layer on the active surface of an ultrafiltration membrane. The Michaelis constant and stability of this immobilized-enzyme system are compared with those of the enzyme either in the native form or immobilized as a dynamically formed gel layer on an ultrafiltration membrane, as previously described by us [Drioli, Gianfreda, Palescandolo & Scardi (1975) Biotechnol, Bioeng, 17, 1365-1367].

Enzymes, Immobilized↗

PubMed1980

Conventional haemodialysis and ultrafiltration: effects on erythrocyte 2,3-diphosphoglycerate and oxygen affinity in patients with uraemia.

1. The relationship between erythrocyte 2,3-diphosphoglycerate (2,3-DPG) and changes in blood pH and in oxygen affinity were studied in six patients treated with two dialysis techniques: conventional haemodialysis and ultrafiltration followed by conventional haemodialysis. 2. The decrease in erythrocyte 2,3-diphosphoglycerate and increase in pH after conventional haemodialysis may significantly increase the affinity of haemoglobin for oxygen and consequently result in inadequate oxygenation of tissue. 3. Ultrafiltration followed by conventional haemodialysis, on the contrary, is more beneficial for oxygenation of tissue and post-dialysis symptoms may be reduced.

Adolescent↗